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Posted at 10:29 AM ET, 02/ 8/2011

January 2011: D.C.'s second straight cold month

By Matt Rogers

Washington, D.C. decadal temperatures averages during January since the 1950s and the average January 2011 temperature.

Our cold winter marches onward. For the second month in a row, Washington D.C. was colder-than-average. But, January 2011 wasn't as strong of a cold anomaly as December as the average temperature at Reagan National Airport was only 1.3F colder than the 30-year (1971-2000) normal.

Like December, I looked at January 2011 in the context of the historical record to see if we can see anything significant. It turns out that January 2011 was the 21st coldest January in the sixty-one year historical record back to 1950. (If you go back to 1871, it was tied for the 56th coldest year with 1910. However, D.C.'s observing site was in different locations prior to the early 1940s when it moved to National Airport.) The average temperature of 33.6F was colder than any decadal average January temperature back to the 1950.

Average annual January temperature in Washington, D.C. 1950 to 2011.

I was surprised to see how warm the 1950s were around here, but warmth was focused the front part of that decade. January 1950 featured the warmest high temperature of the month in DC history- a balmy 79F on January 26! Overall, the 1990s were the warmest decade- it only featured two colder-than-normal winters. You can see the trace of all Washington, D.C. January anomalies on the graph above.

There doesn't seem to be any discernible long-term trend for D.C. and January.

Washington, D.C. also picked up 7.3" of snow in January 2011, which is 1.1" above normal, but that is nowhere near the long-term record 31.5" from the downtown location in 1922. Melted (liquid) precipitation was just 2.25", almost one inch below average.

Jason Samenow pointed out to me that the National Weather Service creates really nifty monthly assessments usually within a week of the close of each month. You can click on your closest airport location here:

Reagan National (DCA)
Dulles Airport (IAD)
Baltimore-Washington (BWI)

I highly recommend scrolling all the way to the bottom for all the fun trivia.

For example, January 2011 at DCA saw 19 of 31 days fail to reach 40F. The coldest low temperature at the airport this month was 17F, which was the coldest reading since February 2010's 16F reading. And this raises an interesting point- the average high temperature was 2.8F below normal, while the average low temperature was 0.3F above normal. The inability to get the low temperatures lower may stem from frequent cloud cover and winds (oh those winds) that kept the surface layer mixed.

From a big picture standpoint, the U.S. saw frequent cold opportunities due to a changing cast of pattern influences in January. The Arctic Oscillation (AO), the North Atlantic Oscillation (NAO), and the Eastern Pacific Oscillation (EPO) all conspired in their negative phases to deliver cold conditions to much of the U.S.

We are finally going to get a break from these powerhouse players next week in a sort of February thaw pattern (highs in the 50s and maybe 60s!?!?), but there are signs that at least the negative NAO could come back to influence our weather late this month into early March.

Historical Washington, DC data provided by NOAA and Speedwell Weather.

By Matt Rogers  | February 8, 2011; 10:29 AM ET
Categories:  Latest, Local Climate  
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   StumbleUpon   Technorati   Google Buzz   Previous: Forecast: Cold and very windy again
Next: No more than flurries likely Thursday


Days of snow on the ground at DCA -

2006-07 = 8 days
2007-08 = 5 days
2008-09 = 5 days
2009-10 = 30 days
2010-11 = 10 days (so far)

Posted by: prayforsnowDC | February 8, 2011 11:06 AM | Report abuse

I remember January 1977 very well. Was living in Pennsylvania at the time, just learning to drive and recall the steering wheel-jarring ice-rutted, potholed roads. Must have been a fair amount of packed snow, though I don't have any records to prove it.

Posted by: bodypolitic | February 8, 2011 11:17 AM | Report abuse

Just hoping that this rather unwelcome mild spell won't [1] dash our chances for a COLD meteorological winter across the board [2] eliminate any more chances of a reasonable snowstorm.

At the beginning of the season I predicted one big storm around Presidents' Day...but don't know if the rather mis-timed "Commuteageddon" two weeks ago was that storm. IMO it would be VERY DISAPPOINTING if we don't get a winter storm around Presidents' Day or in late February...and will be rather tempted to hold Punxsatawney Phil responsible. Groundhog stew, anyone???

On the other side, no further winter storms would make my dance schedule a lot easier...unless "much-unneeded rain" continues to douse my Tuesday nights with raw, CHILLY wind-driven downpours. At least tonight's dry--though too cold and windy for my tastes!

Might also get in my first W&OD trail hike since around Thanksgiving if the weather Sunday gets above 50 after a low above freezing.

Posted by: Bombo47jea | February 8, 2011 12:35 PM | Report abuse

I wouldn't eat that cursed groundhog (blech), but will sign up to help make the soup.

Posted by: FIREDRAGON47 | February 8, 2011 12:42 PM | Report abuse

Mean temperatures for the month don't capture the variability, since a few very warm outliers can drag the mean way up.

Anecdotally, this winter seems to have very few (if any) of those random very nice warm days. If I'm reading the NWS numbers right for National, we had 26 days with a minimum temperature below freezing, which is a +5.3 departure from normal. Seems like persistent cold with no breaks.

Matt, do you have the standard deviation for those years with January's colder than 2011?

Posted by: bryc3 | February 8, 2011 1:27 PM | Report abuse

"There doesn't seem to be any discernible long-term trend for D.C. and January."

Did you try plotting the best fit line to the data, enlarging say the 20 to 50 degree range to make the trend more apparent? Would it perhaps show a line lower on the left and rising to the right from 1954 on.

Together with December, I still think this is the most consistently cold winter I can recall. From the DCA discussion: "THE MOST NUMBER OF SUB-40F DAYS IN JANUARY SINCE 2004...

Posted by: manatt | February 8, 2011 1:42 PM | Report abuse

Manatt, yeah, there might be an uptick if you remove the first half of the 1950s from there.

bryc3, yes, the monthly mean gives you a sense of the prevailing pattern at least. I see a stdev of 1.9F for the 20 years colder than 2011 (back to 1950).

Posted by: MattRogers1 | February 8, 2011 1:59 PM | Report abuse

while i see what you're getting at, what justification could you have for removing the first part of the 50s?

that part DOES seem anomalous. it seems to have less variability than the subsequent years, and seems to be going generally down. what was going on in the 50s?!

why'd you start the graph at 1950? was that just random? i thought that might have been when the measuring station changed, but in re-reading the article i see that the change happened in the early 40s, and that 1950 was the hottest on record. why not start the graph with the change of locations? that's the graph i'd like to see. or did you want to be able to do decadal comparisons?

Posted by: walter-in-fallschurch | February 8, 2011 2:37 PM | Report abuse

Hey Walter, the clean station data I used from Speedwell Weather commenced in 1950. As a meteorologist, I have always felt that 1950 was as far back as you want to go for using decent data, but you make an excellent point. I believe the 1930s-40s were a warmer period around here similar to what they were in the middle of the U.S.

Posted by: MattRogers1 | February 8, 2011 2:49 PM | Report abuse

NCDC recently updated the January monthly rankings too:

Posted by: MattRogers1 | February 8, 2011 2:52 PM | Report abuse

Walter - No justification is needed - the data set you look at determines what you can say. You can't "justify" starting in 1950 either - all you can do is make a statement about the period you are considering: since around 1954, the overall trend is increasing average temperatures. Looking at the data above I can't as easily guesstimate what the trend would be starting in 1950 assuming a straight line. But you also don't need to limit yourself to a straight trend line - you could just as easily say "from 1950 to 1954 the average was decreasing, and has been rising slowly ever since." Language like "no discernible long term trend" is loaded - over 50 years of increasing averages seems "long term" to me. Beware when an author has an agenda, and let the data show what it shows.

Posted by: manatt | February 8, 2011 7:01 PM | Report abuse

Hey Matt, interesting stuff. Why is it you don't feel pre 1950 data is of use? In my mind the switch of locations is fairly unimportant if you're looking for trends and talking differences of a degree or two here and there. Over the course of a few weeks that could be an issue but over multiple decades less so. I know in some instances of indices, hurricane info, etc that pre-satellite data is questionable but I think the thermometer was fairly well perfected by the 1900s! ;)

Posted by: Ian-CapitalWeatherGang | February 8, 2011 8:02 PM | Report abuse

Ian - I have nothing against pre-1950's data and didn't suggest it was of no use (it just wasn't included in the CWG chart above). My point was that you can make a valid statement about data for any period of time as long as you identify the time frame you are referring to (as opposed to using vague claims about the "long term") I agree - go back as far as you can and see what it shows (as noted above "If you go back to 1871, it was tied for the 56th coldest year" - which suggests even when we're cold, we're a lot warmer today.) And I agree - while changing location may have an effect, it doesn't render the older data meaningless. That's supported by the data from just this past month - average high at DCA - 39.7, IAD 37.8, and BWI 37.8 - fairly consistent over a pretty wide area. My point was that if you say "no discernible long term trend" you need more than a plot of decadal averages since 1950 or you're not trying very hard to "discern" a trend. Just looking at the 1950 to date CWG chart above, an increase since 1954 seemed discernible to me with no effort. I'm sure other trends are discernible going back further in time - so go to it team! Andrew Freedman has a caluator too, doesn't he?

Posted by: manatt | February 8, 2011 8:59 PM | Report abuse

i know where matt's coming from, and that's why i asked him about his starting date of 1950. starting the graph with the warmest year sounds like cherry-picking. otoh, if you just lop off the early 50s at the start of the graph, that it seems like cherry-picking too.

speaking of cherry-picking, did you see this last year?

the real funny part starts at 4:47. the wonderfully cherry-picked graph is at 5:34. (btw, we can see in the first 4+ mins. how shameless fox is, no? they're so smugly mocking global warming: look outside... it's snowing today where i am...!)

Posted by: walter-in-fallschurch | February 9, 2011 7:56 AM | Report abuse

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